The present invention relates to a cutting tool holder having a flexible structure, which is loaded on a device such as an industrial robot to enable cutting, and a method for using the same.
Heretofore, studies have been conducted on manufacturing of devices that have “flexibility” provided to the human “hand”, “arm” and “body”. Because of the difficulty of providing the entire device with flexibility, there has been developed a device having “the flexibility” in a state where a part or accessories of the device have high rigidity. Examples of such a device include a device for manufacturing, cutting and carrying soft articles such as sponges, a device for carrying bean curds, and a device for manufacturing bean-jam buns.
On the other hand, as machines and devices in which “the rigidity” is emphasized, there are a variety of machine tools, automobiles, and robots. Many studies have been conducted on achievement of the high rigidity for machine tools. Especially, with regard to a holder for holding a cutting tool, many researches have been made on its structure and material, and in consequence, sharper and more wear-resistant cutting knives have been developed.
By the utilization of the highly rigid blade obtained in the above-described manner, the cutting is carried out, but at conventional machining, the cutting knife is rotated, or a work piece is rotated. In this case, a proper relative speed between the work piece and the blade is secured to increase machining efficiency.
On the other hand, motion of cutting knives is often linear in fields such as chiseling by a carpenter, chiseling in craftworks manufacturing, and scraping in mechanical engineering. Mechanization of such a processing method is often difficult, which delays development of proper mechanical systems and tool holders.
Heretofore, in order to make linear motion (linear swing motion) of a very short distance, development has been advanced on a device for carrying out the cutting in a designated position by attaching the cutting knife to a robot, which acts as a drive unit for driving the cutting knife. However, devices and systems for carrying out the cutting while moving the cutting knife linearly in large movements have not been present yet.
In developing various processing equipments and systems, it is necessary to understand what parameters are the main factors in work by reproducing the work of a skilled hand, based on a variety of information obtained from a working state of the skilled hand. In the methods available thus far, main factors have been considered to be a force applied by the skilled hand, and a cutting speed. The cutting has been carried out by supplying information derived from the two factors to a cutting tool loaded on a highly rigid device.
In such a method, however, it has been difficult to obtain a state similar to a processing result obtained by the skilled hand. There is no doubt that the above two factors are main factors. However, it will be presumed that factors regarding know-how of the skilled hand remarkably affect the processing result. In this connection, however, how to obtain elements constituting the know-how as knowledge has been a serious problem.
Conventionally, a tool having rigidity has been used for the cutting. According to this method, in order to carry out the predetermined cutting, materials have been used having a higher rigidity and volume than necessary. Therefore, if the highly rigid device is directly used for the system for linearly moving the cutting tool, inefficiency occurs in the process of applying a force, and the cutting tool is frequently damaged or broken down to cause great economic loss.
In addition, in the system having the cutting tool attached to the highly rigid machine, work patterns are limited. By combining several limited work patterns, a system called a machining center is constituted. On the other hand, although cutting work carried out by the skilled hand has a problem of efficiency, higher shape accuracy and flatness accuracy can be obtained than by machining. Particularly, in the processing method where the cutting tool is linearly moved, as in the case of chiseling, subtle touching by the skilled hand, and coordinated movements of parts of the body are of great importance in work accuracy. This processing method emphasizes “the flexibility” having both “the rigidity” and “the flexibility” specific to the body of the skilled hand.
The inventors of the present case particularly took up the scraping work by the skilled hand to analyze a cutting force applied to the cutting tool during the cutting, and motion and displacement of a tool 50 at the time. The result is shown in FIG. 8. In FIG. 8, a surface of a material to be cut (a work material) 52 is set as an X-Y plane, a cutting force is applied in the cutting direction (X direction) as Fx, a cutting force is applied in the direction perpendicular to the X direction as Fy, and a cutting force is applied in the downward direction perpendicular to the X-Y plane as −Fz. In addition, reference codes dx, dy and dz respectively denote displacement amounts of the tool 50 in the X, Y and Z directions. In FIG. 8, Fy and dy are not shown.
The skilled hand carries out the scraping work within an extremely short time. By this operation, the skilled hand applies a load on a scraper 51 disposed on the distal end side of the tool 50 by the left hand, and bends the scraper 51 while moving the center of gravity to the right foot, and pulling back the tool to lower a position of the center of gravity of the body. At this time, the distal end (cutting edge) of the tool slightly bites in the surface of the work material 52. The skilled hand carries out the cutting by pushing the entire tool forward while quickly moving the center of gravity from the right foot to the left foot by using a spring-back effect of the tool 50.
Thus, it can be understood that in the scraping work, not only a force is transmitted to the scraper 51 by three-dimensional movement of the body center of gravity of the skilled hand or motion of the arm, but also “flexible” motion of the skilled hand is necessary for providing proper motion to the scraper 51.
However, the conventional industrial robot has been highly rigid and, when a cutting member such as the scraper 51 was directly disposed in the tool holder, it was not easy to carry out processing by reproducing human “flexibility.”